Compare the tensile strength of dry and wet cotton yarns by lea method and calculate their CLSP.

The strength along the length of a body is known as its tensile strength also called linear strength of that body. In the textile fibers or yarns only tensile strength is calculated due to high length to width ratio of the textile materials. The tensile strength values of the dry and wet cotton yarns varies very much from each other. The strength of wet cotton yarns is greater than that of dry cotton yarns. This is due to the formation of hydrogen bonds between the water molecules and the hydroxyl groups in the cellulosic rings of the cotton fibers in the wet state. There is one phenomenon known to stand that when the cotton gets wet its crystalline region increases hence the strength of the fibrous structure increases.

Figure 1: Lea Tensile Strength Tester

The most important properties of a textile product is its mechanical properties. And these properties are a combination of the inherent mechanical properties of the fibers itself and along the manufacturing of a textile product many process increases or decreases these properties. So it is important to consider mechanical properties of the textile materials at every step of the manufacturing process.

Tensile strength is most widely studied mechanical property due to the shape of a textile product. Undergoing through different forces and loads the textile material deforms hence tensile strength of a textile product has a great importance.

So here in this experiment we will find out how to calculate the tensile strength of a cotton yarn using lea method. We will also find out the CLSP values of the dry cotton yarns. CLSP stands for Count Lea Strength Product. It is calculated by multiplying English Count of yarn into its Tensile Strength. It is basically a tool for determining the strength of a yarn. CLSP values in the range of 1800-2200 for cotton are considered good. Lower than 1800 values are considered that the strength of cotton is bad. The experiment is as below:

Objectives:

• To calculate the tensile strength of cotton yarns in both dry and wet state.
• To calculate CLSP of dry cotton yarns.
• To compare the tensile strength of dry and wet cotton yarns.

Materials:

• Dry cotton yarn.
• Water
• Beaker
• Wrapping Reel
• Tensile Strength Testing Machine
• Weighing Balance

Conditions:

Temperature of Dry Yarns = 29 C

Temperature of Wet Yarns = 26 C

Difference in temperature of Dry and Wet Yarns = 3 C

Humidity of the Lab = 70 RH

Procedure:

• Dry cotton yarn was taken.
• 8 leas of 120 yards of that yarn were made using the wrapping reel.
• 4 of them were soaked in the water placed in the beaker.
• Weight of each of the dry samples were taken on the weighing balance.
• These were now placed on the tensile strength testing machine.
• Tensile strength of both dry and wet yarns were calculated.

Calculations:

Length of lea taken = 120 yards

120 yards = 10920 cm

English count = 0.0059 x (length of cm / weight in grams )

CLSP = Count Lea Strength Product = Count x Tensile Strength

Results:

Average Tensile Strength of Dry Cotton Yarns = 83.05 lbs

Average Tensile Strength of Wet Cotton Yarns = 113.85 lbs

% difference in Strength of dry and wet cotton yarns = 27%

Normal range = 10-15 % (According to ASTM standards)

CLSP values of Dry cotton yarns = 1676.81